Apparatus for preparing or conditioning molding materials just prior to their molding



May 22, 1945. R BRdTz c. APPARATUS FOR PREPARING OR CONDITIONING MOLDINGMATERIALS JUST PRIOR TO THEIR MOLDING Original Filed Oct. 15, 1945 I N VEN TOR.

[POM/9N 6' 3180712 A A TWO/ENE]? Patented May 22, 1945 APPARATUS FORPREPARING OR CONDI- TIONING .MOLDING MATERIALS JUST PRIOR TO THEIRMOLDING Roman C. Brotz, Sheboygaii, Wis. original application October15, 1943, Serial No.

Divided and this application February 28, 1944, Serial No. 34,180

5 Claims.

This invention relates to an apparatus for preparing or conditioningmolding materials just prior to their molding and may be used toadvantage with either compression or transfer molding.

This application is a division of my application for Apparatus for andprocess of preparing molding materials for molding, filed October 15,1943, Serial No. 506,399.

Preheating' of the material has been accomplished formerly by the use ofhot air ovens, electrically heated ovens and platens either heatedmaterial at the moment of molding can be acp hed in the most efllcientmanner only if the material is pre-heated to the correct degree beforesubjecting it to additional heat and the molding pressure.

The present invention proposes to speed up the molding cycle and at thesame time to increase the quality of the objects molded, due to higher 1and more uniform density which this process perby steam or electricity.,The disadvantages of sures and heat which subsequently causes it tocure or set as a hard rigid self-subsisting mass. In the case ofthermo-plastic materials, hot fluid molding compounds are'subjected topressure, are formed in warm dies and chilled, or are injected hot intochilled dies to cause them to become rigid sell-sustaining forms.

It is therefore evident that whatever heat and fluidity the materialpossesses before being subjected to heat and pressure in the die, is anadvantage as the time element which this operation requires has beendecreased. If normally, one

pound of thermosetting .molding material requires 100 B. t. u. to cureor set it, and it is possible for the material to absorb 80 B. t. 11.before it is subjectedto additional heat and pressure in a press, thetime element for final curing in the press will require only anadditional B. t. u.

as against 100 B. t. u. had the material been at room temperature whenplaced in the die.

Experience has {:de'monstrated it practical to double and in some casestriple production using the same tools and equipment as was'formerly'used with older methods. Especially is thistrue of injection or transfermolding methods of molding when using thermosetting compounds. In

mits. The extent to which the material is preheated. varies, dependingupon the charging pressure, the area and length of sprues, area of thegates and the curing temperature.

In actual commercial practice it has been found advantageous'to have thematerial approach the same orderas the molding temperature. The materialcan, within certain limits depending upon types of material, and formsto be molded, be preheated above the molding temperature. However, as itis economical and convenient to use the same source of heat as is usedfor the dies or molds, this preheating temperature is usually in thesame neighborhood or range as the molding temperature. f v

To facilitate this desired preheating and the handling of the materialbefore being molded,

the present invention proposes to form up. or

. shape the material before it is placed in the prethis process fluidityplays every important part as the material is placedin a pressurechamber, is subjected to pressure and passed through sprues and gatesbefore finally entering the formin: cavity. ,Fluidityor plasticity istherefore desirable as it ailments 01' assists the molding operation inmanyways. Maximum fluidity of the heater.

This densifying operation is known in the industry as preforming, and isdone for sev,

eral reasons, namely:

1. To decrease the bulk factor of the powder molded by making a pelletor disc tablet.

2. It is easier and cleaner to handle.

3; It simplifies the design or construction of the die as the well orretaining members of the die can be constructed with lessheight tocontain the same weight of charge. This, furtherm'ore, facilitates, thecleaning of the die.

This table g operating is not a new operation in the ind however. Ipropose to provide on the upper an lower plane surfaces of the disctablet a plurality of protuberances or bosses. These bosses are soarranged that when the discs or, tablets are stacked one upon the other,there is, a constant air gap between tablets. This air gap is ofdefinite advantage as it increases the exposed area. of each tablet bythe areas of the upper and lower flats. This is roughly a in stacks.

and handling a. measured charge of tablets.

To better adapt the cartridges for their intended purpose, they areperforated to facilitate the transfer of heat and are also formed with aslot running lengthwise to facilitate the removal of the tablets fromthe cartridge after preheating.

The essential characteristics of the cartridges 'are that they can be soconstructed as to provide for a surface transmission or interchange ofheat, that they be so designed too, so that they may be internallyloaded with a stack or pile of tablets, and that cartridges themselvesmay be piled one upon the other in a vertical manner. One convenient wayof accomplishing this is to provide a 'metal cylinder dimensioned andproportioned to receive a vertical series of tablet filled cartridgesand having surrounding this metal cylinder some source from which heatmay be derived. This source could be an electrical heating element orthe cylinder could be jacketed and hot oil, water, or steam be used forthe heat source. An insulation covering is used over the outside todecrease heat losses. The cylinder through which the cartridges are sentis usually set u vertically so that the cartridges flow through to thebottom by gravity. A swinging gate isprovided at the bottom of thecylinder to support the column of cartridges above, and a cap or coveris provided at the top of the cylinder to prevent a stack of fiue effectduring preforms have greater density and are more uniform in internalstructure.

2. Increased production can be obtained as proper preheating decreasesthe curing time.

3. Moldings of greater intricacy may be madel Longer cored holes can bemolded with a mini mum amount of maintenance.

4. Relatively thick sections can be cured with very little increase incuring time over thin sections.

5. Because of the plasticity of the material one half the moldingpressures may be used to mold the same articles, or twice the number ofarticles may be molded using the same pressures.

With the above recited objects and others of a similar nature in view,my invention resides in the construction, combination, and arrangementof the parts of the apparatus; all as set forth in and falling withinthe scope of appended claims.

In the accompanying drawing, forming a part of this specification:

Fig. 1; is a view in diametrical, vertical, cross section illustratingan apparatus embodying the present invention, parts being shown inelevation for the sake of illustration;

Fig. 2 is a View in side elevation'of the apparatus' shown in Fig. 1,parts being broken away and shown in vertical cross section for the sakeof illustration;

Fig. 3 is a perspective view of one of the pellet holding cartridges;and

Fig. 4 is a perspective view of one of the preforms or pellets of themolding materiah Referring to the drawing it will be seen that the presnt invention proposes to form up or shape the olding material, before itis placed in the preheater, as a tablet or pellet of disk-like form, thepellet or tablet being designated generally at 5 and being shown indetail in Fig. 4. Each pellet 5 has its upper and lower plane surfaces,which are parallel to each other, formed with integral protuberances orbosses 6, angularly spaced from each other, or otherwise so arrangedthat when the discs or tablets are stacked or iled one upon another,there is an air gap between them. As a consequence, when the pellets ortablets are in stack formation ap proximately 100% of their area isexposed.

The pellets 5, when stacked, are received in cartridges designatedgenerally at 1. The stack of pellets in each cartridge 1 provides ameasured charge of molding material. The cartridges 1 are generally orapproximately of cylindrical construction and are constituted of metalof good thermal conductivity. Their body portions are provided with amultiplicity of openings 1; or in other words are of foraminousconstruction to facilitate the transfer of heat. Furthermore, eachcartridge 1 is formed with a slot 8 running lengthwise thereof tofacilitate the removal of the pellets from the cartridge afterpreheating. The lower end of each cartridge 1 is provided with anintegral flange 9 which curves inwardly and then upwardly to provide asupport at the lower end of the cartridge for a pile or stack ofpellets. The upper end of each cartridge is preferably cut away at anangle as illustrated at it) in Fig. 1 to further facilitate handling ofthe pellets, that is, their insertion into and their removal from thecartridge.

The preheater, which is illustrated in Figs. 1 and 2 and designatedgenerally at H, may conveniently comprise an open end cylinder l2,constituted of metal of good thermal conductivity. Usually it isvertically disposed and preferably is located adjacent a molding press.It may be heated in any suitable way. In the construction illustratedthe cylinder i2 is provided with a jacket l3 surrounding itsubstantially throughout its entire extent, the jacket being closed atits end by walls i3, welded or otherwise united and hermetically sealedto the cylinder as well as to the jacket.

An insulated covering i4 is provided for the jacket to decrease heatingloss. An electric heating element could be placed in the jacket butusually it is preferred to circulate a fluid heating medium such as hotoil, hot water, or steam. In fact, in many instances the same heatingmedium that beats the press is also used to heat the jacket. In anyevent, the fluid heating medium is supplied at the upper end of thejacket through an inlet pipe l5 and is carried off at the lower end ofthe jacket by means of an offtake or discharge pipe l6.

A swinging gate designated generally at H is provided at the bottom .ofthe cylinder l2 to support the column of cartridges therein. This gatemay be, as illustrated in the drawing, a circular plate,. suspended bysuitable arms I8, from pivots l9 fixed to and projecting from the Ijacket I 3. The gate, when closed, exercises its supporting function. Itmay be swung to one side of the preheater, to leave the lower end of thecylinder free and unobstructed, thus allowing the cartridges to slideout of the lower end of the cylinder by gravity.

A cap or cover 20 is provided for the upper end of the cylinder and maybe pivotally mounted as at 2| on the jacket. The cap 20, when closed,

' prevent a stack or flue effect through the cylinder l2 during thepreheating operation, and when open allows convenient loading of thecylinder.

While I have shown and described particular examples of the apparatus,it is to be understood that the example has been selected for purposesdiictiyity, e, shiitahie tion to close the lower end oi iiiootrntionrather then iimitetion end thet the indiooted by the oniiended clniine.

Woe-t I cioim is:

i. ii preheoter for molding material coninr'io- 5,

int n verticoi open ended rote ciosing the iower end position ondienving the strncted in another cylinder, o owingnhie of the cylinder inone some open end unobioody end noting when cioeed to prevent or fineetfect through the tuhoior My end when ogcen to niiow charging or theinterior of the body, at eeriee of neiiet-receiving cartridges ofioromi= 7 conetrnction end oi good thormoicondnctivdesigned to iide downthrough the tnnninr ho ly when the note it opened, end to he stinthereinone nhove the other end the note oioeed, end moons for applying hoot tothe roof. 3, nrehenter for nioiding nieterioi commie n rerticoiiydisposed open ended tuouior body constituted of moterioi of good thermoicon- 1 ante combined with the on lower end of the body end noting in onenotithereof and in onother position cover 'shiftably supported on theupper end of eoid tower end anon, n eoyer ohiftnbiy supported on theupper end or 2 nernooo scope of the invention end its verionto oreposition; e. cover pivoted to the too of the cylinder end noting whencloned, io

leaving said lower end open, at I the body and acting when closed toprevent a, fine 4o edect through the ri d end when open to oiiorr iii-:5 or on interior of the My, o eerieo oi neiiet reoeivingg cortrideeeofureminooo conotrnction end oi good thermal conduc- -tirity designed toeiide down through the tithiiior cold iooitet.

i. ii 'preheoter ior molding, moterini comprising o. verticoiiy;disnoeed omen ended cyiinder con- 5 etitiited oi moterioi or goodthennni conductivity,

remoxvehie cioonree ior the code oi the cylinder, meono on the enterioroi the cyiinder tor Meetme the interior thereoi, o. eerieo oi preformreceiving cnrtridyeo contorted one nhore the other in the cylinder endeneh contoinino o stock of proforma, eoid enrtridoee heing oi iornminoueconotroction noting iongitndinoi eioto therein to iociiitnte removoi oithe preheated preform. v

- 5. ii nreheoter. i'or moiding mnteriei comprisme o yortieoiir dieWdopen ended cylinder constinited oi .mntezioi oi good thermoiconductivity, remo oioie cioeoreo tor the endo oi the orilnder, meone onthe exterior oi the cylinder tor interior oi" the hoiiow ho'dy throughthe troii m heating theinterior thereof, series oi preform receivingcortridgeo ennnorted one oioove the other in the cylinder nod coonconteinine' o, stock oi oretorino, said construction end m nimintmniinrdenee nt their iower ends on which to etooit oiprei'orme aresupported end oloo hoyine ienethrriee tioteex tending on through theupper end or the cartridge to rociiitate remove! oi the orehmtedpreforme.

cortridneoheinr oi iorominoue

